22 LIFE PROCESSES-1 NURTRITION, TRANSPORTATION ......Life Processes-1 Nutrition, Transportation, Respiration and Excretion SCIENCE AND TECHNOLOGY Notes the essential raw material that

SCIENCE AND TECHNOLOGY

MODULE - 5 Life Processes-1 Nutrition, Transportation, Respiration and Excretion

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LIFE PROCESSES-1 NURTRITION,TRANSPORTATION,

RESPIRATION AND EXCRETIONThe activities by which living organisms take in food, derive energy, remove wastefrom their body and respond to changes in the environment are called life processes.In this lesson, you will learn about basic life processes, namely nutrition, respiration,transportation of nutrients and fluids in the body, and excretion.

OBJECTIVES

After completing this lesson, you will be able to:

• emphasize the need for energy requirement for life processes;

• explain the steps in photosynthesis;

• appreciate the various modes of heterotrophic nutrition in living organisms;

• realize the importance of the process of nutrition in humans,identify nutritionaldisorders and explain the concept of balanced diet;

• outline the need for and steps in the process of respiration;

• explain the fundamental aspects of transport of material(food, waste etc.) inplants and animals (e.g. humans);

• explain the process of excretion in humans.

I. NUTRITION

22.1 WHY DO WE NEED FOOD

How do you feel if you do not have food for a day or two? You may feel exhausted andweak. But if you do not get food for a few days, will you survive and grow? You willprobably say‘No’. We know that living beings need food to survive. Food provides

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Life Processes-1 Nutrition, Transportation, Respiration and Excretion


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the essential raw material that our body needs to grow and stay healthy. It also providesenergy to carry out various life processes.

In other words, food serves to :

••••• provide energy to carry out life processes, such as respiration, digestion,excretion etc.

••••• help in growth of the body and repair of worn-out and damaged cells andtissues.

••••• help in the production of enzymes and hormones in the body.

22.2 NUTRITION

Nutrition is defined as a process by which living beings obtain food, change foodinto simple absorbable forms and use it to make substances needed by the body.

22.2.1 Types of Nutrition

You already know that only plants can make their own food. Animals eat plants or otheranimals. There are two main modes of nutrition—autotrophic nutrition and heterotrophicnutrition.

a) Autotrophic nutrition (autos: self; trophos: food)

The green plants, algae and cetain bacteria manufacture their own food throughphotosynthesis. They are termed autotrophs and their mode of nutritionautotrophic nutrition.They are the producers of the food chain as all organismsdepend for food on them.

b) Heterotrophic nutrition (heteros: different; trophos: food)

The organisms, which depend on other organisms for their food, are called heterotrophsand their mode of nutrition is heterotrophic nutrition.

Heterotrophic nutrition is of various types

(i) Holozoic nutrition (Gk: holos = whole; zoic = animal)

Holozoic nutrition includes ingestion, digestion and absorption of food as in Amoeba,frogs and human beings.

(ii) Parasitic nutrition: Have you ever been bitten by a head louse or a bed bug or hadworms inside the body? These organisms that live on or inside other living organisms,and derive their food from them are called parasites and the nutrition is calledparasitic nutrition. Cuscuta or Dodder plant (Amar bel) is a parasite on green plants.



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(iii) Saprotrophic nutrition: You must have seen a white cottony growthdeveloping on your wet leather shoes or belts especially when they get wet duringrainy days. This is a fungus. The fungus grows and feeds on substances, whichwere once part of the living organisms, such as stored food, wood, leather androtten plant products. Some common examples are mushrooms, bread mould,yeast, etc. Organisms that derive their food from dead and decaying organismsare called saprotrophs. Saprotrophs help in cleaning the environment bydecomposing the dead and decaying organic matter.

INTEXT QUESTIONS 22.1

1. Give two examples of autotrophs. Why do you call them so?

___________________________________________________________

2. Why are autotrophs termed ‘producers’ of food chain?

___________________________________________________________

3. Fill in the blanks in the flow chart given below:

Types of Nutrition

4. The parasitic and saprotrophic modes of nutrition do not need the three processesrequired by holozoic animals. Which processes are these?

___________________________________________________________

5. Classify the following as saprotrophs or parasites: leech, yeast, head louse,mushroom

___________________________________________________________

22.3 NUTRITION IN PLANTS—PHOTOSYNTHESIS

(Photo :light; synthesis : make)

Photosynthesis is ‘a biochemical process by which green plants manufacture their ownfood using carbon dioxide and water as raw materials in the presence of sunlight andchlorophyll’. Oxygen is released as a by-product in this process.


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Photosynthesis is the only process by which solar (sun’s) energy is convertedinto chemical energy. The overall equation of photosynthesis is given here.

2 2 6 12 6 2 26CO 12H O C H O 6H O 6O+ ⎯⎯→ + + ↑Carbon dioxide Water Glucose Water Oxygen

22.3.1. Essential raw materials for photosynthesis

i. Chlorophyll

To carry out photosynthesis, plants require as raw materials, carbon dioxide(CO

2), water (H

2O), light and chlorophyll. Light gives energy for photosynthesis.

Photosynthesis takes place in chloroplasts in the cells of leaves. The greencolour of plants is due to chlorophyll. Chlorophyll is in the chloroplasts. It can traplight.

ii. Sunlight

Sunlight is absorbed by chlorophyll as solar energy.

iii. Carbon dioxide and water

Carbon dioxide and waterare combined in thechloroplast with the help of anumber of enzymes to yieldsugar which is converted intostarch. Oxygen formedduring photosynthesisdiffuses out into theatmosphere through thestomata (Fig.22.1).

22.3.2 The mechanism of photosynthesis

Photosynthesis occurs in two steps— (i) the light reaction and (ii) the dark reaction. Inthe light reaction, light is captured by chloroplast. The reaction occurs in the chloroplasts.In the dark reaction glucose is formed. Dark reaction occurs in chloroplasts. The darkreaction and light reaction occur simultaneously.

What happens to the end products of photosynthesis?

• As seen in fig.22.1, glucose is formed in photosynthesis. It is either used upby the cells or is converted and stored in the form of starch. The other endproduct oxygen is released into the atmosphere. Energy is released duringphotosynthesis.

Fig. 22.1 Photosynthesis in a leaf



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22.3.2 Significance of Photosynthesis

i. Photosynthesis is responsible for providing food to all living beings.

ii. Carbon dioxide produced during respiration by all living beings is used upduring photosynthesis and does not accumulate in the atmosphere.

iii. Oxygen released during photosynthesis is used for respiration by livingbeings.


1. In two sentences, justify the term photosynthesis (photo+ synthesis).

___________________________________________________________

2. What makes plants look green? What does the green pigment of plants do forthem?

___________________________________________________________

3. Glucose and starch are two food substances manufactured in the plants.Which one is formed during photosynthesis and in which form is it stored.

___________________________________________________________

4. What role does stomata play in photosynthesis?

___________________________________________________________

22.4 NUTRITION IN HUMANS

The food that we eat, consists of many different items of food. You may prefer totake more of one type of food and less of another. Does your diet fulfil your body’srequirement? Does it satisfy your taste buds or body needs? Think.

For healthy growth and development of the body, you need to eat food thatprovides enough of all essential nutrients. What does the term nutrient mean?

Nutrients are the chemical substances present in our food which nourish ourbody.

Nutrients are broadly divided into three groups.

(i) Energy-yielding nutrients—carbohydrates and fats

(ii) Body-building nutrients —proteins and

(iii) Growth-regulating nutrients—vitamins and minerals


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a) Carbohydrates

Carbohydrates are the main source of energy in our diet. Carbohydrates may be in theform of sugars, starch or cellulose.

Dietary carbohydrates

Types of Carbohydrates Source

Sugar Fruits, milk, sugarcane

Starch Potato, wheat, rice, sweet potato

Cellulose (Roughage) Salads and raw vegetables

b) Fats

• Keep the body warm.

• Help in the transport of fat-soluble vitamins

• Some common sources of fats are edible oil, ghee, butter, meat and nuts likegroundnuts.

• One gram of fat on oxidation given about 37 kilo joules (9 kilocalorie) ofenergy.

edible oil, ghee, butter, meat and nuts like groundnuts

c) Proteins

You must have often heard your mother insisting on your having a glass of milk or a bowlof cooked pulses (dals) or an egg. All these are rich in proteins. Growth of body tissuesis the main function of proteins.

d) Vitamins

You have often heard your mother saying ‘Eat carrots and your eyesight will improve’.This is because carrots contain vitamin A. What are vitamins? Table 22.1 lists certainvitamins. They are necessary for normal growth, and maintenance of the body, and arerequired in relatively small amounts. Deficiency of a particular vitamin causes disease.Overdose of certain vitamins, such as vitamins A and D, is harmful.

Vitamins may be water-soluble or fat-soluble.

Water-soluble: Vitamins B—complex (B1, B

2, B

4, B

12) and C

Fat-soluble: Vitamins A, D, E and K



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Table 22.1: Types of vitamins, their sources, functions and deficiency diseases

Vitamin Sources Functions Deficiency disease

A

Milk, carrots, tomatoes, egg.

keeps eyes and skin healthy.

Night blindness (Poor vision in dim light)

B1

Milk, peas, cereals, green vegetables, meat

Growth and development

Beri-beri (a disease which affects the nervous system)

B12

Liver, eggs, milk, fish Form red blood corpuscles

Anaemia (deficiency of red blood corpuscles)

C

Amla, tomatoes, citrus fruits, water chestnut(Singhara)

Healthy growth, strong blood vessels

Scurvy (a disease in which gums swell up and bleed)

D

Sunlight, milk, whole grains and vegetables

Form strong bones and teeth

Rickets (a disease which affects bones in children making them soft and deformed)

E

Vegetable oils, milk, butter, whole grains, vegetables

Protects cell membranes

Affects fertility

K

Green vegetables like spinach and cabbage

Helps in the clotting of blood

Excessive bleeding from wounds

e) Minerals

Minerals such as iron, calcium, sodium, potassium, iodine etc.are required by the bodyin small quantities. Table 22.2 indicates the sources and functions of some importantminerals.

Table 22.2: Some important minerals, their sources and functions

Minerals Sources Functions

Iron Green leafy vegetables, turnip, sprouts, yeast, liver, eggs, meat

Forms haemoglobin,

Calcium Milk and milk products Forms strong bones and teeth, and needed for muscle movement, clotting of blood

Potassium Green and yellow vegetables For growth and keeping osmotic balance of cells and blood

Iodine Sea food, iodized salt Body metabolism, development of brain

f) Water

Water is an important part of our diet. It makes 65-70% of our body weight. Waterregulates the body temperature, and provides is a medium for biochemicalreactions taking place in the body.


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g) Raw vegetables

Raw vegetables help in bowel movement. They form the ‘roughage’ needed to preventconstipation.

22.4.1 Balanced diet

Now that you are aware of the components of diet, try to analyze your own food intake.Do you include all the food components in your diet?

For healthy growth and development, you need to eat foods that provide all the essentialnutrients in the correct proportion. Eating a variety of foods in proper quantity everyday constitutes a balanced diet. A balanced diet contains adequate amounts of essentialnutrients such as carbohydrates, fats, proteins, vitamins, minerals and water. Theproportion may depend on age, sex, pregnancy etc.

ACTIVITY 22.1

Make a list of food that you consumed in the last seven days. Tabulate as shown below.Discuss with your parents/friends/siblings if your diet is balanced, if not, work towardsmaking it balanced.

Day Food taken Nutrients taken Items containing the nutrients

1 2 3 4 5 6 7

Lunch Carbohydrates Protein Fats Vitamins Minerals

1 2 3 4 5 6 7

Dinner Carbohydrates Protein Fats Vitamins Minerals


1. Why should raw vegetables and fruits be a regular item in lunch/dinner?

___________________________________________________________



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2. I ate one gram of starchy food and you ate one gram of fatty food—who shall getmore energy you or me?

___________________________________________________________

3. What is common between vitamins A and D and B and C to group themtogether?

___________________________________________________________

22.5 DIGESTION-THE PROCESS OF NUTRITION INHUMAN BEINGS

The food that we eat cannot be used by the cells in the body in the form in whichit is eaten. Conversion of complex food material into smaller substances so thatit can be absorbed by the cells is called digestion. Taking in of food is termedingestion.

22.5.1 The digestive system

Alimentary canal is a longcontinuous tube constitutedmade by mouth, pharynx,oesophagus, stomach, smallintestine, large intestine, andrectum. The glandularorgans, salivary glands, liverand pancreas and thealimentary canal form thedigestive system. (Fig.22.2)

22.5.2 Enzymes

The process of digestionrequires enzymes present inthe digestive juices secretedby the organs of digestivesystem. They convert complex substances into simpler ones. Enzymes are chemicalswhich speed up chemical reactions taking place in cells. Almost all enzymes arecomplex proteins and remain unchanged during the chemical reaction. They can,therefore, be used repeatedly.

Fig. 22.2 Alimentary canal in human beings

Oesophagus


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22.5.3 Processes involved in nutrition

The entire process of nutrition includes the following steps: ingestion, digestion,absorption, assimilation and egestion.

a) Ingestion and digestion

The process of taking in food through the mouth is called ingestion. The digestion offood starts from the mouth and ends in the small intestine.

i. Mouth: Carbohydrates, such as starch, are broken down or digested to formsugar. Saliva contains an enzyme salivary amylase that breaks down starch intosugar. It also helps in lubricating the food and making it easier for swallowing.

ACTIVITY 22.2

Taste a piece of bread or chapatti by biting it. What is the taste? Now chew well withteeth and roll with tongue. What is the taste now and why?

ii. Oesophagus: There is no digestion in this part, also called gullet .The oesophagusor the food pipe by the contraction of muscles in its wall pushes the food into thestomach. Muscle movement is termed peristalsis and helped food travel down thealimentary canal.

iii. Stomach: The stomach is a highly muscular organ. The gastric glands present inits walls secrete gastric juice containing hydrochloric acid (HCl) and enzymes likepepsinogen. HCl activates pepsinogen into pepsin and kills bacteria. Proteins arebroken into smaller fragments called peptones by the enzyme pepsin.

iv. Small intestine: The food moves from the stomach to duodenum, which is theupper part of the small intestine. Emulsification of fat (fat is broken into fat droplets)takes place with the help of the bile juice secreted by the live and stored in gall bladder.Bile does not have any digestive enzymes but it creates an alkaline medium whichis essential for the action of pancreatic enzymes.

The pancreatic juice contains three enzymes.

• Trypsin—converts peptones and proteoses to smaller peptides.

• Amylase—converts starch into maltose.

• Lipase—converts fats into fatty acids and glycerol.

The digestion of proteins into the end products amino acids, carbohydrates intoglucose, and fats into fatty acids and glycerol is completed in the small intestine.

The inner surface of the small intestine contains thin finger-like projections calledvilli, which increase the surface area for absorption of digested food into the blood



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capillaries lining the villi. The blood then carries the absorbed food to different parts ofthe body and undigested food is pushed into the large intestine.

Jaundice is caused by liver infection

When a person suffers from jaundice, the skin looks pale with a yellowish tintdue to large amounts of bilirubin a bile pigment in the blood. The urinebecomes deep yellow. Jaundice is caused by the Hepatitis virus. The virus isof different types and now there is an injection that provides immunity from thevirus. The infection usually comes from infected water.

v. Large intestine: This part of the body absorbs water from the undigestedfood and solid waste is lubricated to form the faeces. The faeces pass on to thelower part of the large intestine, called the rectum, and are thrown out of the bodythrough the anus.

b) Absorption

Blood capillaries in the villi pick up digested food and take it to all cells.

c) Assimilation

The absorbed food supplied to cells is used to release energy and also to build upthe cell components. This is called assimilation.

d) Egestion

The process by which the undigested food material or waste is released from thebody is called egestion.

ACTIVITY 22.3

Prepare a chart with the figure of alimentary canal and write down one or two mainevents of digestion occurring in front of each part. For example, in front of thestomach you can write

HCl Acidic medium⎯⎯→

PepsinProtein Peptones⎯⎯⎯→

It will help you understand and remember.


1. Name the enzyme secreted by stomach that converts proteins into peptones.

___________________________________________________________


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2. What is the movement of muscles of oesophagus that pushes down foodcalled?

___________________________________________________________

3. In which part of the alimentary canal do the pancreas and liver pour theirsecretions?

___________________________________________________________

4. Name the enzymes present in the pancreatic juice that digests proteins,carbohydrates and fats.

___________________________________________________________

5. Name the acid that takes part in digestion process.

___________________________________________________________

22.6 DEFICIENCY DISEASES OR NUTRITIONALDISORDERS

A disease that occurs due to lack of adequate and balanced diet is called deficiencydisease.

Intake of improper or inadequate diet in human beings is called malnutrition.Malnutrition is harmful for children as it retards their mental and physical growthDeficiency diseases due to inadequate nutrition are of three types:

a. Protein Energy Malnutrition (PEM)

b. Mineral deficiency diseases

c. Vitamin deficiency diseases

a) Protein Energy Malnutrition (PEM)

Deficiency of proteins in the diet causes PEM. This is the prime reason why yourparents insist that you should drink milk; eat pulses and other sources of proteins.Two diseases caused due to PEM are – Marasmus and Kwashiorkor (Fig. 22.3a, b).

i. Marasmus

It affects children up to one year of age. This occurs inchildren deprived of mother’s milk. The symptoms of thisdisease include:

• loss or wasting of muscles,

• body develops loose folds of skin,

• ribs become prominent, Fig.22.3(a) Child sufferingfrom Marasmus



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• body growth and development slows down.

It can be cured by ensuring mother’s milk for infants and by having a diet rich in protein,carbohydrates, fats, vitamins and minerals.

ii. Kwashiorkor

Amongst children of age group 1-5 years, protein deficiencycauses kwashiorkor. The symptoms of this disease are:

• enlargement of liver due to water retention,

• darkening of the skin with scaly appearance,

• hair becomes reddish-brown,

• legs become thin, and

• retardation of physical and mental growth.

Eating a protein-rich diet that consists of milk, meat,groundnut, soyabean, jaggery, etc. can cure this disease.

b) Mineral deficiency diseases

The two common mineral deficiency diseases are – goitre and anaemia.

i. Goitre: Caused due to prolonged iodine deficiency which causes enlargementof thyroid gland. Iodized salts and seafood are good sources of iodine. (seefigure 23.11 in the lesson-23, Control and Coordination)

ii. Anaemia: Iron deficiency causes lesser production of haemoglobin(respiratory pigment), resulting in anaemia. An iron-rich diet consisting ofspinach, apple, banana, guava, eggs, groundnuts, etc. can help to cureanaemia.

c) Vitamin deficiency diseases

You have already studied about vitamins and their deficiency diseases intable 22.1.

22.6.3 Food Adulteration

Why do we prefer to buy food products sold in sealed packets and items madeby a standard reliable company? A simple answer is that the manufacturerselling its products in sealed packets or brands ensures delivery of good qualityproduct.

Any attempt to mix items of food with cheaper, sub -standard, edible or inediblesubstances is called food adulteration. Table 22.3 shows adulterants of differentfood items

Fig. 22.3(b) Child sufferingfrom Kwashiorkor


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Table22. 3: Some food items and their common adulterants

Food item Common adulterants

Cereals Straw, husk, stones, inferior quality grains, infected orinsect infested grains

Pulses Straw, kesari dal, inferior quality grains, infected grains,metanil yellow dye

Milk Starch, water, milk of other animals, extraction of fats,synthetic milk

Edible oils Mineral oil, argemone oil, artificial colours

Turmeric (haldi) Starch coloured with chromate or metanil yellow dye

Coriander Powdered cow/horse dung, saw dust, starch

Black pepper Dried papaya seeds

ACTIVITY 22.4

Food Adulteration

Take any five food items present in your house eg. pulses, rice, channa, black pepper,wheat, coriander seed etc. look for the various adulterants (if any) present in each ofthe five food items. Now state whether these adulterants are edible or inedible. Recordyour observations in a tabular form.


1. Give the full form of PEM and name the diseases due to PEM.

___________________________________________________________

2. If the diet continuously lacks in vitamin A, which disease may be caused?

___________________________________________________________

3. Why does our government frequently advertise the necessity of consumingiodised salt?

___________________________________________________________



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22.7 TRANSPORTATION

The distribution of food and oxygen to all parts of the body as well as removal ofbody wastes is performed by a transport system within the body of all livingorganisms. Our body also secretes many hormones, which have to be carried totheir target organs. The flow of fluid (blood or lymph) within the body for transportpurposes is termed circulation and the organs for circulation constitute circulatorysystem.

22.7.1 Transport of Materials in Plants

(i) Transport of water

Roots of plants take up water and minerals from the soil. How does this watermove up from roots to leaves for photosynthesis? You have already learnt aboutconducting tissues of plants – xylem and phloem in lesson 21.

Tracheids and vessels, which are non-living cells of xylem, transport water pickedup by root hairs (Fig.22.4) from soil to the leaves.

The upward movement of water and minerals from soil termed ‘ascent of sap’ isagainst gravity and is due to transpiration pull. Transpiration is the process inwhich a lot of water evaporates (as water vapour) from stomata. This evaporationcreates a vacuum and pulls up water through the xylem. This is transpiration pull.

(ii) Transport of food material

Sugars and other food molecules synthesized in the leaves are transported to other partsof the plant through phloem. Sieve tubes are living cells of the phloem, which transportfood (Fig.22.5). Transport of food material from leaves to other parts of the plant iscalled translocation. This food may then be stored in fruits, stem or roots.

Fig.22.5 Sieve tubes in phloemFig.22.4 Root hairs


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22.8 TRANSPORTATION IN HUMAN BEINGS

Human circulatory system consists of

(i) Centrally located muscular pump called heart, and

(ii) Blood vessels, which are tube-likestructures, connected to the heart(Fig.22.6).

Blood vessels are of three kinds:

• Arteries: Carry blood from heartto various parts of body.

• Veins: Bring blood from variousparts of body to the heart.

• Capillaries: Thin vesselsbetween the artery and the vein.The capillaries allow the exchangeof materials between blood andtissues.

(iii) Circulating fluid—blood, tissue fluid and lymph

22.8.1 Heart

Heart is a powerful muscular organ lying between lung. It is four-chambered- two (rightand left) atria (sing. atrium, also called auricles), and two (right and left) ventricles. (Fig.22.7a).

Fig. 22.7(a) The human heart

The heart is made of specialised muscle cells, also called cardiac muscle fibers,which contract and relax all the time without getting tired. The contraction and

Fig. 22.6 Arteries, veins and capallaries



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relaxation follows a rhythm called heartbeat. Heart pumps blood into the bloodvessels.

Rhythmic heart beat results in the proper transport of substances to the variousorgans by means of blood. In one minute, normal human heart beats about 72times. Abnormalities in heartbeat can be seen by taking ECG or Electrocardiogram(Fig. 22.7b).

Fig. 22.7ECG or Electrocardiogram

The oxygen laden blood from the leftventricle gets pumped into a large arterycalled aorta. It carries oxygenated bloodto all parts of the body. The general planof human circulatory system is given inFig 22.8

ACTIVITY: 22.5

Find out the addresses of three hospitals/clinics/nursing home nearest your housewhere treatment for heart diseases istaken up.

You must have noticed that veins bringoxygen depleted and carbon dioxide ladenblood to the heart and arteries take oxygenladen blood away from the heart. But hereare two exceptions – the pulmonary arterycarries carbon dioxide laden blood and thepulmonary vein carries oxygen laden blood.

Blood Pressure

It is the force with which blood pushes against the walls of the arteries. It isgenerally measured in terms of how high it can push a column of mercury. Whenventricles contract, pressure of blood inside the arteries is highest. In a healthy

Fig.22.8 General plan of the humancirculatory system


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young human being, it is about 120 millimetres of mercury (120 mm Hg). Whenthe ventricles relax, pressure of blood inside the arteries is comparatively less Itis about 80 millimetres of Hg (80 mm Hg) in a healthy young man. Thus, a healthyyoung man has a normal blood pressure of 120 / 80 mm of Hg. The instrument usedto measure blood pressure is called sphygmomanometer.

Pulse rate

The systemic contraction of the heart can be felt as a jerk in certain arteries like theradial artery in the wrist and neck artery below the jaw which are superficial inposition. This is called arterial pulse. Pulse rate is the same as the rate ofheartbeat.

ACTIVITY 22. 6

Locate and hold the radial artery present in your wrist. Try and count the numberof beats in a specified time. It is called ‘pulse’ and will give you an idea of thenumber of times your heart beats in a minute.

ACTIVITY 22. 7

Visit the local medical centre and get your pulse rate and blood pressure checkedand also that of your family members. Do you find any difference in blood pressureand pulse rate of your family members?


1. Why is a system of transportation/circulation necessary for organisms?

___________________________________________________________

2. Which kind of blood vessels are responsible for the exchange of nutrients andrespiratory gases between blood and tissues?

___________________________________________________________

3. What is so special about heart that it continues beating without getting fatigued?

___________________________________________________________

22.8.2 Circulatory Medium

Our body has three different types of fluids

• Blood—found in heart and blood vessels (arteries, veins and capillaries)



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• Tissue fluid—found in spaces between cells in organs

• Lymph—found in lymph vessels and lymphatic organs (e.g. spleen and tonsils)

Blood

Blood is a connective tissue that circulates throughout the body. It is made up ofa fluid medium called plasma in which float two types of blood cells, called redblood cells, white blood cells and cell fragments called blood platelets. Bloodcells are manufactured in the bone marrow. (Fig.22.9)

Fig22.9. Types of blood cells

(a) Red blood cells (RBC or Erythrocytes)

• These are circular in shape, and contain a red coloured pigment calledhaemoglobin

• No nucleus is present in RBC

• RBC carry oxygen to tissues and bring back carbon dioxide from tissues

(b) White blood cells (WBC or Leucocytes)

• Since they carry no pigments, they are colourless

• They have irregular shape

• They prevent body from infections by eating up germs or by producingantibodies to fight antigens.

(c) Blood platelets (Thrombocytes)

• These are very small fragments of cells

• They have no nuclei

• They participate in clotting of blood

Functions of blood: Blood carries nutrients, oxygen, carbon dioxide, hormonesand waste material to the relevant parts of the body. Some medicines when takenin the body are also distributed through blood.


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22.8.3 Blood groups and blood transfusion

You must have heard that blood has to be arranged for a person undergoing asurgery (operation) or in the case of an accident or in case of persons sufferingfrom thallasemia. This arrangement is to replace blood lost from the patient.Injecting blood into the body from outside is called blood transfusion. Bloodtransfusion is successful only when the blood of donor (who gives blood) andof the recipient (who receives blood) match. Unmatched blood transfusioncauses agglutination (clumping together) of red cells due to which the recipientmay even die.

On the basis of types of proteins present in the blood, a system of blood groupsknown as ABO system having four blood groups named A, B, AB and O isrecognized in human blood (Table22.4). Antigens present on membrane of RBCof transfused blood is counteracted by antibodies present in the plasma of recipient.

Table 22. 4: Human blood groups and their compatibility

Blood Antigens on Antibodies in Can donate Can receivegroup RBC plasma blood to blood from

A A b A, AB A, O

B B a B, AB B, O

AB AB None AB A, B, AB,O

O None a, b A, B, AB, O O

The persons with blood group O can donate blood to all and so ‘O’ group is calleduniversal donor and AB group can receive blood from donors of all blood groupsand is called universal recipient. Can you say why?

22.8.4 Lympthatic system

Lymph is also a circulatory fluid and flows in the lymph vessels.

• It is light yellow in colour.

• It always flows only in one direction from tissues to heart.

• Cells called lymphocytes present in lymph eat up germs and prevent bodyfrom infections.

• It returns proteins and fluids from circulation to tissues.

22.8.5 Disorders related to circulatory system

1. Heart attack: Like all other organs, heart also needs nutrients and oxygen.When arteries supplying the heart become thick due to age or faulty diet



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consisting of excessive fatty food, muscle cells of the heart cannot beat in theproper rhythm. Heart attack occurs which can be detected in an abnormalECG. Immediate medical attention is then required.

2. Anemia: When haemoglobin level falls below a certain point, the conditionis called anemia. It makes the person weak and look pale and inactive. Ironin the diet helps remove anemia.

3. Leukemia: This is blood cancer. The bone narrow makes excessive WBCsand few RBCs.

4. Hypertension: It is another term for high blood pressure and leads to headache,dizziness and fatigue. Normal blood pressure is 120/80. Proper diet, exercise,medicines and tension free mind helps to cure high blood pressure.


1. Which blood cells would you categorise as (i) transporters of oxygen andcarbon-dioxide (ii) enemies of germs that enter the body.

___________________________________________________________

2. Sheena has blood group O+ and Veena has AB+. Whose blood would beuseful if it has to be transfused into an accident victim of unknown bloodgroup and why?

___________________________________________________________

3. What makes RBC s look red? What is the role of this pigment?

___________________________________________________________

4. In which function is lymph similar to blood?

___________________________________________________________

22.9 RESPIRATION

We can live without food for s everal days but we cannot live without breathingeven for a short while. Breathing provides oxygen to the cells of our body foroxidation of food in order to generate energy for various activities.

22.9.1 Respiration in Plants

Plants do not have any special respiratory organs. Roots take up oxygen from airtrapped in the soil by means of root hairs. Root hairs are embedded in the soil.Oxygen in the air surrounding them diffuses into the root hair and from there into


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the roots. Carbon dioxide given out, similarly, diffuses out through roots. Stomata inleaves opens to let in oxygen and release carbon dioxide.

In the older parts of roots or bark of woody plants, tiny openings called lenticels arepresent. It is through these lenticels that oxygen reaches the inner living tissues andcarbon dioxide moves out.

Fig22.10 Opening and closing of stomata (showing inner and outer surface)

Guard cells help in the opening and closing of stomata. When guard cells get filled upwith water, they swell and become turgid. The two guard cells curve away from eachother opening the stomata. When guard cells become flaccid, stoma closes. Mineralsalso play a role in making guard cells turgid or flaccid.

22.9.2 Breathing and Respiration in humans

Respiration may be divided into two steps.

• Breathing involves inhalation of air containing oxygen and exhalation of carbondioxide.

• Cellular respiration is responsible for release of energy by oxidation of food(glucose), and its conversion into ATP (adenosine triphosphate)—The energymodule.

Respiration is different from breathing.

Breathing is the physical process of respiratory gaseous exchange between theorganism and the environment by diffusion. It takes place in the lungs. On theother hand, respiration involves oxidation of food and release of energy whichtakes place in the cells along with respiratory gaseous exchange.

22.9.3 Respiratory system in Humans

Respiratory system

Respiratory system of human beings has the following parts (Fig22.11).



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• External nares or nostrils.

• Nasal cavities inside thenose.

• Internal nostrils opening intopharynx.

• Pharynx that leads into thewind pipe or trachea.

• Trachea divides into twobronchi (one bronchus)which lead into the two lungs.

See figure 22.11 and locate the trachea,the windpipe

The opening of the pharynx into the trachea is called glottis. Trachea is thinwalled but its walls do not collapse even when there is not enough air in it as it issupported by rings of cartilage. Trachea bifurcates into bronchi.

Lungs enclose within them branches of bronchi called bronchioles which branchfurther and end in very thin walled sac-like structures called air sacs or alveoli(sing. alveolus). See the figure of respiratory system.

The voice box or larynx is present on the trachea

22.9.4 Mechanism of breathing or ventilation of lungs

Lungs are located in the chest cavity or the thoracic cavity. Below the chest cavityis the abdominal cavity. These two cavities are separated from each other by adome-shaped (upwardly arched) muscular sheet called diaphragm (see figure22.11).The movement of diaphragm helps in breathing. Breathing, also called ventilationinvolves two processes:

(i) Inhalation (drawing the air inwards) (Fig.22.12a) is the result of increase inthe volume of the thoracic cavity. This increase is caused by the changes that takeplace in the position of diaphragm and ribs.

• Diaphragm straightens out due to contraction of its muscles.

• Ribs are raised upward and outward and volume of chest cavity enlargesby contraction of rib muscles.. As volume of chest increases pressure ofair in it decreases.

• Atmosphereic air rushes in and reaches the alveoli. It brings in oxygenwhich diffuses into the capillaries from the alveoli.

(ii) Exhalation (Fig 22.12b) is the result of decrease in the volume of the thoraciccavity.

Fig. 22.11 Respiratory system in human beings


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This decrease in the volume is caused when:

• Diaphragm relaxes and resumes its dome shape, arching upwards.

• Ribs are lowered downwards and inwards.

• Thoracic cavity is compressed and the pressure inside the lungs is increased.

• The alveolar carbon dioxide diffuses out and is pushed out through thetrachea and nose.

• This breathing out of carbon dioxide laden air is called exhalation.

If you take long breaths, you can feel your chest go up and down.

22.9.5 Breathing Rate

When at rest, an adult human breathes about 16 to 18 times per minute. Breathingrate increases during physical exercise, disease, fever, pain and under stress.

ACTIVITY 22.8

Check your breathing rate at rest. Now run for 5 minutes or climb 15 stairs and thencheck breathing rate. Do you find any difference? You will observe that you startpanting and your rate of breathing increases as you run or climb the stairs.

Fig22.12. How the thorax changes shape during breathing



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22.9.6 Exchange of gases between blood and tissues

Inhalation fills in the alveoli of lungs with oxygenated air. This oxygen has toreach the various tissues of the body. Thus as the first step, blood capillaries onalveoli (Fig22.17) pick up oxygen from alveoli and carbon dioxide brought by thecapillaries from the tissues is exchanged for oxygen. Oxygen diffuses into alveoli.

In the tissues, oxygen gets used up and carbon dioxide is accumulated which isnow exchanged for oxygen in blood. The carbon dioxide picked up by blood fromtissues is carried to the heart by veins.

Fig.22.13 Exchange of gases between blood and alveoli

22.9.7 Cellular Respiration

Once inside the tissues, oxygen acts upon the digested food (glucose) which hasreached the cells of the tissues. As a result energy and carbon dioxide arereleased. This occurs in the mitochondria of the cells and is called cellularrespiration.

Do you know why mountaineers and sea divers carry oxygen cylinders andwear oxygen masks? As we climb higher and higher altitudes, the air pressurebecomes lower and lower. Reduced oxygen supply causes breathing troublesand oxygen masks facilitate breathing. People living in hilly areas haveevolved adaptation such as increased number of red blood corpuscles and largethoracic cavity. Divers carry oxygen masks because we derive our respiratoryoxygen from air and not water.

Artificial respiration

A victim of an accident like drowning, electric shock or inhalation of poisonousgas suffers from “asphyxia” or lack of oxygen. The symptoms are blueing of lips, fingernails, tongues and stoppage of breathing. In such cases mouth-to-mouth respiration is given.

You must have realised how important respiration is for survival. Medicaltechnology has introduced certain gadgets like the “oxygen mask” and“ventilators” which assist the patient in respiration during breathing problems.Often these help the patient to overcome such problems.


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1. Why does the trachea not deflate (collapse) during exhalation?

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2. The sequence of parts of human respiratory are jumbled. Place them in theright order. Nasal cavity, trachea, pharynx, internal nostrils, bronchi, lungs.

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3. You have learnt in Physics that when volume increases, pressure decreases.How does this principle find a place in the process of breathing?

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4. Once oxygen reaches cells, which of its organelles takes over respiration?

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5. Why are the alveoli supplied with capillaries?

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IV EXCRETION

Many chemical reactions take place inside body cells. Some products of thesechemical reactions are not needed by the body. They may even be harmful ifthey accumulate in the body. Their removal from the body is called excretion.

22.10 HUMAN EXCRETORY SYSTEM

In human beings, excretion is carried out by an organ system known as the urinarysystem or the excretory system. Seethe figure (Fig 22.14) and locate thefollowing parts:

• Two bean shaped kidneys,located below the diaphragm inthe abdomen and towards theback.

• Two excretory tubes or ureters,(one from each kidney).

• One urinary bladder, uretersopen into it.

Fig.22.14 Human excretory system



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• A muscular tube called urethra arises from the bladder. The urinary openingis at the end of urethra.

22.10.1 Structural and functional unit of the kidney — Nephron

Each kidney is made of tube like structures called nephrons (renal tubules). Anephron is the structural and functional unit of the kidney. The cup-shaped upperend of nephron is called Bowman’s capsule, has a network of capillaries withinit called glomerulus. Glomerulus is a knot of capillaries formed from the arterywhich brings blood containing wastes and excess of water to the kidney. Bowman’scapusle leads into a tubular structure. The tubular part of the nephron or renaltubule has three sub-parts, the proximal convoluted tubule (PCT), a thinner tubecalled loop of Henle and the distal convoluted tubule (DCT) (Fig. 22.15). Bloodcapillaries surround these tubules.

22.10.2 Mechanism of excretion

Filtration and reabsorption are two importantprocesses of excretion.

Blood entering the glomerulus gets filtered in theBowman’s capsule and is called the nephric filtrate.The red blood corpuscles and proteins do not filterout. (Fig 22.15a) .They remain in the blood stream

The filtrate entering the renal tubule not onlycontains waste but also useful substances. Theuseful substances get reabsorbed from the tubuleinto the blood capillaries surrounding thetubule. Excess water and salts like sodiumand chloride also get reabsorbed into theblood from the renal tubule. Thus, wastealone which is primarily in the form of ureaenters into collecting tubules from variousrenal tubules. It is the urine.

From the kidneys, the urine enters the ureters to reach the urinary bladder whereit is temporarily stored. Urine is thrown outperiodically through the urinary opening.

Functions of kidneys

• Kidneys not only excrete nitrogenouswastes but also regulate the water contentof the body (osmoregulation), and

Fig.22.15(a) Bowman’s capsule

Fig.22.15 (b) Structural and functionalunit of the kidney— Nephron


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• Keep the normal mineral balance in the blood. When this balance is upset, a personcan fall sick.

22.10.3 Other organs that remove waste from our body

Apart from kidneys, lungs, skin and liver also remove wastes. Sweat glands in the skinremove excess salts when we perspire. Lungs remove carbon dioxide Fig. 22.16.

Fig. 22.16 other excretory organs

22.10.4 Maintenance of the internal environment

A person gets sick if the balance of substances such as mineral ions, water or evenhormones inside the body is upset. Maintenance of the correct amount of waterand mineral ions in the blood is termed osmoregulation.

22.12.5 Kidney failure, dialysis and kidney transplant

Certain diseases or sometimes an accident may lead to kidney failure. Since thenumber of nephrons is as large as almost one million in each kidney, a person cansurvive even with one kidney. However, in case both the kidneys are damaged, itis difficult to remain alive. Modern technology can now save such patients withthe help of new techniques like dialysis and kidney transplant. Fig. 22.17 showsthe set up of an artificial kidney. A tube is inserted in an artery in the patient’s armor leg. The tube is connected to the kidney machine. This plastic tube has twomembranes so as to form one tube within the other. In the inner tube flows bloodfrom patient’s artery. This blood is surrounded by fluid (dialysis fluid) in the outertube, separated from it by the membrane of the inner tube. Wastes move out ofblood into the fluid. The blood cleaned of its waste goes back from the kidneymachine into the vein in the arm or leg and back into the body. The dialysis fluidcarrying waste is removed from the machine. This technique is termed dialysis.



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Nowadays, a surgeon may sometimes remove a non-functioning kidney from apatient and replace it with a kidney donated by another person. Care, however, hasto be taken so that a foreign kidney gets accepted by the body of the recepient.

Fig22.17 Artificial Kidney


1. Name the organ of the excretory system, which stores urine before its removal fromthe body.

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2. Draw a rough diagram of the nephron and label only the part where filtrationoccurs?

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3. What happens to the useful substances that move into the glomerulus alongwith nitrogeneous waste?

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WHAT YOU HAVE LEARNT

• Nutrition is a process by which living beings procure food or synthesize it andchange it into simple absorbable form by a series of biochemical processesin the body.


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• The photosynthesis provides food for all. It is the ultimate source of energy for allliving organisms. It is essential for sustaining life.

• A balanced diet contains adequate amount of essential nutrients such ascarbohydrates, fats, proteins, vitamins, minerals and water. The amount ofthese nutrients in diet depends upon a number of factors, such as age, sex andnature of work an individual performs.

• Conversion of complex food material into smaller substances so that it canbe absorbed by the cells is called digestion. The digestive system enablesconversion of ingested food into its simpler form. The process of digestionrequires a number of enzymes.

• The absorption of food occurs mainly in the small intestine. The simplesoluble food molecules are absorbed from the small intestine into the bloodwhich takes them to all the cells of the body.

• A disease that occurs due to lack of adequate and balanced diet is calleddeficiency disease. Deficiency diseases caused due to malnutrition are ofthree types: protein energy malnutrition (marasmus and kwashiorkor); mineraldeficiency diseases (goitre and anaemia); and vitamin deficiency diseases(xerophthalmia, rickets, beri-beri, pellagra).

• The distribution of food and oxygen to all parts of the body as well as theremoval of body wastes is performed by a transport system within the bodyof all living organisms.

• Heart in humans is four-chambered, two upper chambers are called atria andlower chambers are ventricles. Heart is made of cardiac muscle fibres.

• Every human being belongs to one of four blood groups: A, B, AB and O.Blood transfusion can be between matching blood groups. The persons withblood group O can donate blood to all and ‘O’ group is called universal donorand AB group can receive blood from all and is called universal recipient.

• Breathing is the physical process of respiratory gaseous exchange betweenthe organism and the environment by diffusion. On the other hand, respirationinvolves oxidation of food and release of energy along with respiratorygaseous exchange.

• In human beings, excretion is carried out by an organ system known as theurinary system or the excretory system.

• A nephron is the structural and functional unit of the kidney.

TERMINAL EXERCISES

1. Multiple choice type questions.



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i. Rickets is caused due to deficiency of:

a) Iron

b) Vitamin D

c) Proteins

d) Carbohydrates

ii. One gram of a substance was oxidized. The energy released amounted to9.0Kcal. The substance was of the type:

a) Carbohydrates

b) Fats

c) Vitamins

d) Proteins

iii. A person living in the hilly regions of Shimla developed swelling in his neckregion. The doctor said his thyroid gland got swelled up. Name the nutrientdeficient in his diet.

a) Calcium

b) Iron

c) Phosphorus

d) Iodine

iv. The vitamin that helps in the clotting of blood is:

a) Vitamin A

b) Vitamin D

c) Vitamin E

d) Vitamin K

v. In human beings, gas exchange between the environment and the body takesplace in the :

a) larynx

b) bronchi

c) alveoli

d) trachea

vi. RBCs of human beings who live in high altitude regions:

a) increase in number

b) decrease in number

c) decrease in size

d) increase in size.


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vii. Lungs have a large number of alveoli for:

a) maintaining a spongy texture and proper shape.

b) more surface area for diffusion of gases.

c) more nerve supply.

d) more space to increase volume of inspired air.

viii. The main function of lymph is to:

a) transport O2 to the brain.

b) transport CO2 to lungs.

c) return interstitial fluid to blood.

d) return RBCs and WBCs to lymph vessels.

2. Name the following.

i. A fluid that transports fatty acid and glycerol.

ii. The valve present in between the chambers on the right side of the humanheart.

iii. The respiratory pigment present in RBCs.

iv. The iron containing pigment in RBCs.

v. The phase of cardiac cycle in which the auricles contract.

3. Give on epoint of difference between the following.

1. Autotrophic and heterotrophic nutrition

2. Breathing and respiration

3. Arteries and veins

4. Blood and lymph

5. Auricular systole and ventricular systole

4. Match the columns A and B.

COLUMN A COLUMN B

1. Sponge-like organs located in the chest cavity a. trachea

2. Chamber acting as a common passage for food b. bronchiolesand air

3. Elastic tissue that forms a flap over the top of c. epiglottisthe larynx

4. Main passageway to the lungs d. pharynx

5. Small tubes that branch from the bronchi e. bronchi

6. Small air sacs in the lungs f. lungs

g. alveoli

h. larynx



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5. Given below is an example of a certain structure and its function.

‘Kidney and excretion’

Fill in the blanks on a similar pattern.

1. Alveoli and ____________

2. Diaphragm and ____________

3. ‘C’-shaped cartilage rings and ____________

4. Erythrocyte and ____________

5. Left ventricle and ____________

6. Pacemaker and ____________

6. What is a balanced diet? Name three items of a diet that provide three differentnutrients?

7. What are the main steps of photosynthesis? Is sunlight essential for photosynthesisand why?

8. A patient complains of lack of appetite, exhaustion and is losing weight. Diagnosethe deficiency. What kind of diet would you suggest for the patient?

9. Deficiency of which vitamin causes night blindness. What would you suggest toprevent this deficiency?

10. Where does the digestion of starch, proteins and fats take place and what is therole played in digestion by liver and pancreas?

11. Which component in your diet will not be digested if the enzyme lipase is notsecreted?

12. Explain how oxygen leaves the blood from the tissue capillaries and carbondioxide enters the blood in the tissue capillaries.

13. Explain the usefulness of large surface area provided by alveoli for respirationin human beings.

14. Why do arteries have a thick or elastic wall?

15. What are the four types of blood groups present in humans? Prepare a tablewith two columns to show the different human blood groups and names ofcompatible blood groups in the other column.

ANSWER TO INTEXT QUESTIONS

22.1

1. Green plants, algae and bacteria (any two); they undertake photosynthesis tomanufacture their own food.


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2. They are the food for all the oorganisms in a food chain

3. Types of nutrition: Autotrophic, Heterotrophic:—Holozoic, Parasitic, Saprophytic/saprotrophic

4. Digestion of the ingested food.

5. Parasitic: leech, head louse; saprophytic: Yeast, mushroom.

22.2

1. Photo means light and synthesis means manufacture. Plants manufacture food inpresence of light.

2. Chlorophyll; necessary for photosynthesis.

3. Glucose during photosynthesis stored as starch.

4. Let in CO2, from the atmosphere

let out

O

2 is to the atmosphere.

22.3

1. Easy bowel movement / prevents constipation/, forms roughage.

2. You

3. Vitamin B and C.—Water soluble vitamin

Vitamin A, D, E and K.Fat soluble:-

22.4

1. Pepsin

2. Peristalsis/ peristaltic movement

3. Small intestine

4. Trypsin digests proteins, Amylase digest carbohydrates, Lipase digests fats

5. HCl (Hydrochloric acid)

22.5

1. Protein Energy Malnutrition; Marasmus and Kwashiorkor

2. Night blindness; Beri Beri, Pellagra; Anaemia, Scurvy; Rickets; Excessive bleedingfrom wounds (any two)

3. Because it contains Iodine which is necessary for formation of thyroid hormones/prevention of diseases due to deficiency of thyroid hormone/prevention of goitre.



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22.6

1. To circulate O2 / products of digestion of food/ removal of waste

2. Capillaries

3. Valves prevent mixing of oxygen laden blood with carbon dioxide laden blood.

22.7

1. (i) RBC

(ii) WBC

2. Sheena’s blood because O group is universal donor.

3. Haemoglobin; carries oxygen to tissues and brings back carbondioxide fromtissues.

4. Prevent body from infections; returns proteins and fluid from circulation totissues.

22.8

1. It is supported by rings of cartilage.

2. Nasal Cavities; Internal nostrils; Pharynx; Trachea; Bronchi; Lungs.

3. During inhalation, chest cavity enlarges and air pressure in it decreases so air fromoutside rushes in.

• Diaphragm straightens out.

• Ribs are raised upward and outward

• Volume of chest cavity increases;pressure of air is it decreases

• Air rushes into the alveoli

4. Mitochondria

5. For the exchange of gases (O2 and CO

2)

22.9

1. Urinary bladder

2. Bowman’s capsule labeled in the figure of nephron.

3. Get reabsorbed into the blood capillaries surrounding the tubule.

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22 LIFE PROCESSES-1 NURTRITION, TRANSPORTATION ......Life Processes-1 Nutrition, Transportation, Respiration and Excretion SCIENCE AND TECHNOLOGY Notes the essential raw material that